This document describes how to use an infrared proximity sensor to measure distance with an Arduino board. The sensor outputs an analog voltage between 3.1V at 10cm and 0.4V at 80cm that is read by the Arduino. The sketch declares variables for voltage and distance, initializes serial communication, reads the analog voltage from the sensor, converts it to a distance using the sensor's formula, prints the distance to the serial monitor, and delays to display results over time as the distance changes. When run, the circuit successfully measures distances from 10cm to 80cm as demonstrated in the serial output.

1. 1
Arduino Tutorial #4
- Measuring the distance -
Dong Ho Son
POSTECH
Pohang, Korea
donghoson@postech.ac.kr

2. 2
Measuring the distance - Overview
 Infrared proximity sensor (GP2Y0A21YK0F)
• A sensor to detect the presence of nearby objects without any physical contact
• The sensor has an analog output that varies from 3.1V at 10cm to 0.4V at 80cm
 How the circuit works
• Infrared proximity sensor will sense the distance and send the result to the
Arduino board
• A serial monitor shows the distance from the sensor to the target object
Source: commons.wikimedia.org/wiki/File:Sharp_GP2Y0A21YK_IR_proximity_sensor.jpg

3. 3
Measuring the distance – configuring the circuit
 Configure the circuit
VOC
GND
Vout
Source: pixabay.com/photo-2168193

4. 4
Measuring the distance - Sketch
 Declare variables
• float Vcc = 5.0;  Voltage
• float dist;  Distance
 setup() { }
• Serial.begin(9600);
− Prepare the serial communication to get
the value of distance (from the sensor)
− 9600 : serial communication speed
– 9600 bits per second is the default for the Arduino

5. 5
Measuring the distance - Sketch
 loop() { }
• dist = Vcc * analogRead(A0) / 1023;
− Read analog value of infrared distance
− analogRead(A0) returns the value as 10 bit
− 210=1024, 0~1023 values are returned
− Dividing the output by 1023  the distance
• dist = 26.549 * pow(dist, -1.2091);
− Formula [Distance = 26.549 × 𝑉𝑜𝑙𝑡𝑎𝑔𝑒−1.2091]
http://image.dfrobot.com/image/data/SEN0014/gp2y0a21yk0f.pdf

6. 6
Measuring the distance - Sketch
 loop() { }
• Serial.print(“ Dist = ”);
− It prints the text “ Dist = ” to the serial console
• Serial.print(dist);
− It prints the value of ‘dist’ to the serial console
• Serial.println(“ cm ”);
− It prints the text “ cm ” to the serial console
− Also changes the line (newline)
• Delay(300);
− Need 300ms to check step-by-step

7. 7
Measuring the distance - Result
 The sensor measures the distance!
10cm
Dist = 10.00 cm
20cm
Dist = 20.00 cm
Dist = 40.00 cm
40cm
Dist = 80.00 cm
80cm
VOC
GND
Vout
Source: pixabay.com/photo-2168193